In burst switching, a source node sends a burst transfer request to a core node to indicate that a burst of data is coming, the size of the burst and the destination of the burst. Responsive to this burst transfer request, the core node configures a space switch to connect a link on which the burst will be received to a link to the requested burst destination. In a first scheme, the burst follows the burst transfer request after a predetermined time period (a scheduling time) and it is expected that, when the burst arrives at the core node, the space switch will have been properly configured by the core node. In a second scheme, the source node waits for a message from the core node, where the message acknowledges that the space switch in the core node is properly configured, before sending the burst.
Often core nodes are used that do not have buffers to buffer incoming data. Core nodes without buffers are desirable because: it may not be possible to provide buffers without an expensive optical-electrical conversion at input and electrical-optical conversion at output of an optical space switch; and the core node may be distant from the source and sink (edge) nodes, therefore requiring remote buffer management in an edge-controlled network.
In the first scheme, a burst may arrive at a core node before the space switch is properly configured and, if the core node does not include a buffer, the burst may be lost. Furthermore, until the source node fails to receive an acknowledgement of receipt of the burst from the burst destination, the fact that the burst has been lost at the core node is unknown to the source node. Having not received acknowledgement of receipt of the burst, the source node may then retransmit the burst. In the second scheme, the time delay involved in sending a burst transfer request and receiving an acceptance before sending a burst may be unacceptably high, leading to low network utilization. Despite these shortcomings, burst switching is gaining popularity as a technique to transfer data in high-speed networks since it simplifies many of the control functions and does not require capacity to be reserved when it may not always be in use. Furthermore, burst switching reduces a need for characterizing the traffic. Clearly, a burst switching technique that allows for greater network utilization is desirable.